# Skip-check-slave-lag is not working for pt-online-schema-change

**URL:** <https://forums.percona.com/t/skip-check-slave-lag-is-not-working-for-pt-online-schema-change/22060>\
**Category:** Percona Toolkit\
**Tags:** mysql, percona\
**Created:** [May 15, 2023, 10:36am UTC](https://forums.percona.com/t/skip-check-slave-lag-is-not-working-for-pt-online-schema-change/22060 "2023-05-15T10:36:54Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![izavadinskiy](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/izavadinskiy/32/10596_2.png) [@izavadinskiy](https://forums.percona.com/u/izavadinskiy)\
**Post date:** [May 15, 2023, 10:36am UTC](https://forums.percona.com/t/skip-check-slave-lag-is-not-working-for-pt-online-schema-change/22060/1 "2023-05-15T10:36:54Z")

</div>

Hi.  
Guys, I am trying to use **pt-online-schema-change** for changing table structure to **utf8mb4**.  
Faced with the issue when pt-online-schema-change showing the exception about “Cannot connect to h=10.3.15.0,p=…,u=” (slave host.)  
Found that we can use --skip-check-slave-lag argument to skip connected slaves.  
But unfortunately this option doesn’t work for me.  
When we just specifying --skip-check-slave-lag without DSN it continue checking the slaves:

```auto
Found 1 slaves:
ip-10-3-2-60 -> slave_ip_address:socket
Will check slave lag on:
ip-10-3-2-60 -> slave_ip_address:socket

```

When we specifying the DSN like

```auto
--skip-check-slave-lag h=ip_addess,P=3306

```

It returns us that something could not be parsed exception:

```auto
Use of uninitialized value in string eq at /usr/bin/pt-online-schema-change line 8867.

```

The whole command that we are using is below:

```auto
pt-online-schema-change --alter 'CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci' --host={$host} D="{$DB}",t={$table},u="{$user}",p="{$password}" --no-drop-old-table --preserve-triggers --execute --no-check-replication-filters --skip-check-slave-lag h={$slave_ip_addr},P=3306 --alter-foreign-keys-method=rebuild_constraints --critical-load Threads_running=500

```

Please advise how we can properly use --skip-check-slave-lag.

---

<div class="post-metadata">

**Author:** ![Ivan\_Groenewold](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/ivan_groenewold/32/6299_2.png) [@Ivan\_Groenewold](https://forums.percona.com/u/Ivan_Groenewold)\
**Post date:** [May 15, 2023, 11:04am UTC](https://forums.percona.com/t/skip-check-slave-lag-is-not-working-for-pt-online-schema-change/22060/2 "2023-05-15T11:04:25Z")

</div>

Hi, you can try --recursion-method=none this should ignore any replicas

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<div class="post-metadata">

**Author:** ![izavadinskiy](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/izavadinskiy/32/10596_2.png) [@izavadinskiy](https://forums.percona.com/u/izavadinskiy)\
**Post date:** [May 15, 2023, 11:08am UTC](https://forums.percona.com/t/skip-check-slave-lag-is-not-working-for-pt-online-schema-change/22060/3 "2023-05-15T11:08:46Z")

</div>

Hi Ivan. Thanks for so quick response.  
I suppose this option works.

```auto
Not checking slave lag because no slaves were found and --check-slave-lag was not specified.
Operation, tries, wait:
  analyze_table, 10, 1
  copy_rows, 10, 0.25
  create_triggers, 10, 1
  drop_triggers, 10, 1
  swap_tables, 10, 1
  update_foreign_keys, 10, 1

```